In the processing of halogen-containing thermoplastic resins, such as polyvinyl chloride (PVC) and polyvinylidine chloride, to form moldable or extrudable formulations, it is customary to incorporate into the polymeric resin a variety of additives for special purposes to achieve desired processing properties as well as desired properties in the molded or extruded products. Often, the processing properties and properties of the product go hand-in-hand, for example, good rheological properties contribute to minimal resin degradation during mixing or extrusion and less color in the product composition. Among additives typically employed are lubricants, pigments, heat and light stabilizers, light-filtering materials, antioxidants and the like.
Lubricants are added to halogen-containing thermoplastic resin formulations for the purpose of improving rheological properties of the mixture, both before and after fusion. Lubricants are typically classified as external lubricants, which are insoluble in the resin and act to lubricate the interaction of separated resin products, and internal lubricants which are soluble in the resin. There is, however, not necessarily a sharp demarcation between internal lubricants and external lubricants, and lubricants, such as the lubricants described herein, may be partially soluble in the resin and serve both internal and external lubricating functions. Because the lubricants described in this invention are primarily used in substitution of conventional external lubricants, the lubricants according to the invention are referred to herein as "external lubricants". Typical external lubricants used in the industry are synthetic hydrocarbon paraffin waxes having melting points of about 160.degree. F. (71.degree. C.). To a lesser extent, low molecular weight mineral oils having low viscosities have been employed as external lubricants in conjunction with paraffin waxes.
In preparing fused compositions from mixtures that include halogen-containing thermoplastic resins, there exists continual problems of discoloration. Discoloration is typically caused by degradation of the resin itself, but may be caused in part by degradation of additives as well. The interaction of degradation products and additives also determines the course of color development in thermoplastic resins. A variety of materials, including the stabilizers and lubricants are available to inhibit color formation. The particular stabilizers and lubricants optimal for particular formulations and processing conditions generally must be empirically determined. Stabilizers are typically selected from organo-tin and organo-antimony compounds plus a variety of costabilizing compounds which enhance the stabilizing ability of the organo-tin and organo-antimony compounds, examples of such costabilizers being found in U.S. Pat. Nos. 4,360,619, 4,115,352, 3,647,748, 3,398,114, 3,507,827, 3,933,744, 4,269,731, 4,256,618, and 4,314,934.
There exists the need for novel lubricants for processing halogen-containing resins. Novel lubricants are expected to improve rheological conditions during processing of the formulation and thereby reduce degradation and color formation. As is the case with stabilizers, different specific lubricating compounds tend to be optimal for different particular thermoplastic formulations.